That ticket (6847) has been closed as “invalid”, but I don’t understand why–I suspect that the person who closed it didn’t realize that it doesn’t seem to work with Atom or RSS2 because of https://core.trac.www.ads-software.com/ticket/8706.
The patch that mystyman suggested works because of the inconsistency in 8706; the person who marked 6847 invalid is correct about how it /should/ work, but not about how it currently /does/ work, and until 6847 is fixed mystyman’s patch looks like the right answer to me.
Also, here’s another forum thread on it:
https://www.ads-software.com/support/topic/192997.